[extropy-chat] HISTORY: Solved & Unsolved Riddles

[scerir]

John K Clark:

> 7) What does the wave Quantum Mechanics associates
> with every particle really mean?

That's simple: a big mess :-)

"I like to emphasize that light comes in this form - particles.
It is very important to know that light behaves like particles,
especially for those of you who have gone to school, where you
were probably told something about light behaving like waves.
I'm telling you the way it *does* behave - like particles."
- R.P.Feynman, "QED", p.15

"Particles do not exist, only waves and wave packages. We
speak not of 'particles and waves' but of 'detectors
and waves'"
- P.J. van Heerden, Amer. Journ, of Physics, 43, (1973), p.1015.

"Each photon then interferes only with itself. Interference
between two different photons can never occur."
- P.A.M. Dirac, Principles of Quantum Mechanics, Clarendon, Oxford,
1930, p.15. [Unfortunately the last sentence is dead wrong,
and the first is imprudent]

"The question of whether the waves are something "real" or a function
to describe and predict phenomena in a convenient way is a matter of
taste. I personally like to regard a probability wave, even in
3N-dimensional
space, as a real thing, certainly as more than a tool for mathematical
calculations ... Quite generally, how could we rely on probability
predictions if by this notion we do not refer to something real and
objective?"
- Max Born, Dover publ., 1964, "Natural Philosophy of Cause and Chance",
p. 107 [Brilliant!]

So, the above is enough to say that the experimental *smooth* transition
between the wave-like and the particle-like behaviour forbids an
interpretation which acknowledges the status of only one of the two
properties of the "entity". Either both or none. And none is difficult.
(The "entity" is governed by the Greenberger & Yasin inequality,
or other similar inequalities.)

In general the "entity" can be seen as a carrier of information, of
a *finite* quantity of information. In an interferometer we produce
a change in the "entity" (say photon) state vector, which has 
degrees of freedom (i.e. spatial, and spin). Thus we produce
a subtle change in that (finite) quantity of information the 
"entity" was carrying before. Any 'which-way' marking (in an 
interferometer, i.e. by means of polarizers) contains two degrees 
of freedom and produces a correlated state like |s1,p1>+|s2,p2>, 
where s1,s2 are informations (or 'images') about the leg of the 
interferometer, and p1,p2 are informations about the polarization 
state. Thus if you change the informations you may also expect
some change in the behaviour of the "entity".

Zeilinger wrote about it at http://arxiv.org/abs/quant-ph/0201026
and this seems to be a possible good description, if not solution.

But, of course, now the riddle becomes: the superposition principle!